The present disclosure generally relates to the filtration of a fluid containing platelets. More specifically, the present disclosure relates to a filtration unit to selectively remove leukocytes from a fluid containing platelets, and systems comprising such a filtration unit.
Whole blood is formed of two types of components: first, blood cells comprising red blood cells, leukocytes and platelets, and second, plasma, which is a pale yellow liquid in which the blood cells are suspended.
Currently, only necessary blood components are transfused to patients. For example, only platelet concentrates are transfused to patients suffering from thrombocytopenia, who have a reduced amount of platelets in the blood.
It has been found that leukocytes have rather significant undesirable effects, which has led to attempts to eliminate them from blood components intended for transfusion. In fact, leukocytes increase the risk of immune rejection, such as graft-versus-host disease, and promote the transmission of infectious agents. It has also been demonstrated that leukocytes negatively affect platelet preservation.
To eliminate leukocytes from blood components intended for transfusion, filtration units enclosing a leukocyte-removal medium are generally used. In such units, the leukocyte-removal medium comprises one or more membrane(s) and/or one or more layer(s) of non-woven material made of a polymer material and treated to improve the rate of leukocyte removal, the recovery of the blood components, the priming time for filtration, and/or the selectivity of the filtration.
Such filtration units may improve the selectivity of the filtration, for example, by allowing platelets to pass through the leukocyte-removal medium. To eliminate leukocytes while still allowing the platelets to pass through, a number of polymer surface treatments of leukocyte-removal media have been proposed. For example, U.S. Pat. No. 4,936,998 describes a filter medium for selectively eliminating leukocytes. The filter medium is formed of fibers coated with a polymer containing non-ionic hydrophilic groups and basic functional groups containing nitrogen. Such a polymer is, for example, a copolymer of hydroxyethyl methacrylate and diethylaminoethyl methacrylate.
In addition, EP 1230940 describes a filter for eliminating leukocytes while allowing platelets to pass through the filter. The filter comprises a substrate, the surface of the substrate being at least 70% coated with a synthetic hydrophilic polymer having a mass average molecular mass between 300,000 and 3,000,000. As in document U.S. Pat. No. 4,936,998, the polymer is a copolymer containing non-ionic hydrophilic groups and basic functional groups containing nitrogen, obtained, for example, by copolymerization of hydroxyethyl methacrylate and diethylaminoethyl methacrylate. EP 1230940 also provides that when the filter is coated with a polymer having a mass average molecular mass below 300,000, the rate at which platelets pass through the filter is reduced.
JP 7-25776 proposes a filter for selectively eliminating leukocytes, comprising, on its surface, a polymer provided with a polyethylene glycol chain and hydrophobic portions. In EP 1452193, it is explained, however, that this polymer, due to the increased quantity (59-74 wt %) of ethylene oxide chains, poses the risk of eluting the polymer into the blood. To solve this problem, document EP 1452193 suggests using a polymer obtained from: (i) a hydroxyalkyl (meth)acrylate, (ii) a monomer containing basic nitrogen groups, and (iii) a monomer comprising ethylene oxide chains containing between 2 and 9 repetitions of ethylene oxide. The mass average molecular mass of the polymer is greater than 100,000 so as to avoid elution problems.
Another filtration unit is described in U.S. Patent Application Publication No. 2006/0207937. Said unit comprises a filter coated with a polymer obtained by reacting a hydrophobic monomer and a hydrophilic monomer. The surface of the filter has a critical wetting surface tension (CWST) between 50 and 80 dyn/cm. For example, the polymer may be a copolymer of vinyl acetate and vinylpyrrolidone. The polymers have a mass average molecular mass (Mw) between 10,000 and 200,000 g/mol, preferably between 20,000 and 100,000 g/mol.
It has also been proposed in WO 2007/054638 to coat a leukocyte-removal medium with a linear polymer of the Poloxamer® type having a molar mass between 2,000 and 18,000 g/mol. This type of polymer coating, however, leads to elution problems.